High frequency transmitter



y w. BUSCHBE CK v 2,250,571

HIGH FREQUENCY TRANSMITTER Filed April 13, 1959 M O DULA T/ON SOURCE /f SH/F'TER 'P INVENTOR WERNER BUSCHBE'CK ATTORNEY Patented July 29, 1941 1 UNITED STATES PATENT ()FFICE I f 2,250,571. V HIGH FREQUENCY TRA'NsMI'i T n Y Werner Buschbeck, Berlin; Germany, assignor to y g Telefunken Gesellschaft fiir.Drahtlose Tele-' graphic in. b. H., Berlin, Germany, a corporation of Germany Application April 13, 1939, Serial No. 267,585 In Germany March 26, 1938 4 Claims. (01. 179-1715) The invention relates to a high frequency inal audio frequency potentials i. e. only the potransmitter in which reduction of distortion tentials which correspond to the distortions in through counter coupling of the low frequency the tube and its circuits. These potentials are component is obtained by detection of the moduapplied to the grid circuit of the tube R where lated oscillations appearing in the output. It is 5 they effect a compensation of the distortions. known to bring about a distortion reduction by Since the detector G does not operate strictly counter coupling of the audio-frequency and a linearly for high modulation percentages, the indifference voltage formed by the audio frequency vention proposes to couple in thedetector circuit appearing in the output and by the original modadditional carrier frequency oscillations derived ulation potentials. The audio-frequency is obfrom the carrier frequency source T and applied tained by the detection of the high frequency to the detector circuit by means of the coupling oscillations derived from the output circuit. It coil K. Phase shiftingmeans P is provided in was found, that at very high degrees of modulathe circuit. The phase relationship between the tion of the transmitter a satisfactory distortion modulated and unmodulated currents is so adreduction cannot be brought about and that adjusted that the resultant percentage modulation ditional distortions appear Whose cause was at is Within the range handled by the detector G first not known. The invention is based upon with minimum distortion. Aside from the conthe teaching that these distortions which are trol setting of the phase relationship between the produced at high degrees of modulation can be modulated currentand the unmodulated current, traced to the fact that the detection in the de-- in addition a control of the amplitude may be tector rectifying the output potential is not linear carried out in this circuit so that the degree of so that in this detector additional distortions apmodulation of the modulated high frequency popear rendering impossible a complete compensatentials appearing at the detector G can be tion of the other distortions. These dimculties chosen as desired. can be eliminated in accordance with the present The invention is not limited to the example of invention in a simple manner in that the deconstruction shown and may be used in the gree of modulation of the high frequency oscilvarious circuits in which it is necessary to return lations appearing in the output circuit and apand rectify the potentials derived from the outplied to the detector is decreased by the applicaput of a discharge tube circuit.

tion of carrier oscillations so that the detector I claim: instead of having to detect fully modulated oscil- 1. The method which includes the steps of imlations, need be used only for the detection of pressing modulating potentials on high frequency oscillations whose degree of modulation may be oscillations to obtain modulated high frequency as low as desired. In this case a completely oscillations, adding a portion of said high frelinear operation of the detector can be easily quency oscillations to a portion of said moduachieved, since its characteristic can always be lated high frequency oscillations in a desired maintained linear over a small range. In the phase relationship whereby a modulated oscillacase of highly modulated oscillations linear detion of a lower percentage of modulation is protection over the entire range may be accom duced, rectifying said last mentioned modulated plished only under great difficulties. 4o oscillations to produce additional alternating The invention will be elucidated with refercurrent components and superimposing said adence to the accompanying figure which shows an ditional alternating current components on said embodiment of the invention. Herein is shown modulating potentials in a desired phase relaitem M the modulation source and item T, the tionship, source of the carrier frequency both operating 2. In combination, a source of carrier waves, upon the transmitter tube R contained in any a modulator tube, a source of modulating waves, desired modulation circuit. The high frequ n y means for feeding carrier and modulation waves oscillations are derived from the output circuit from said sources to said modulator tube, a rectiof the tube R and applied to a detector G. The fier, means for feeding modulated wave energy detector is connected to the one diagonal of t e from said modulator tube and means for feedbridge circ i 1 to the other diagonal of which ing unmodulated carrier wave energy from said the o i n l modulation potentials r pplied. carrier wave source to said rectifier, and means Then in the one branch of the bridge, for infor additionally modulating carrier wave energy stance in Z, there appears the difference of the from said carrier Wave source with the output of potential derived from the output and the origsaid rectifier,

feeding unmodulated carrier wave energy from said carrier frequency source to said rectifier, a"

circuit through which the output of said recti- 4. In a signalling system an electron discharge tube having input and output circuits, 2. source of modulating potentials, means for subjecting input electrodes of said tube to said modulating wave potentials, means for additionally subjecting input electrodes of said tube to waves from a carrier frequency oscillation source, an output circuit connected to output electrodes of said tube, a rectifier coupled to said output cir- '*cuit, a circuit for feeding unmodulated carrier frequency wavejrom said carrier source to said rectifier and means for subjecting the input elecfier flows for additionally modulating carrier wave energy fed from said carrier frequency source to said tube.

' said rectifier.

trodes of said tube with the rectified output of WERNER BUSCHBECK. 

